Director Harald Zwart spoke about his choice of Orvarsson for the film stating, "I came out of a screening of another film Atli previously scored and there was a certain energy about it. I thought 'He's the perfect man for the job." Based on the fantasy world of Shadowhunters, Orvarsson created several themes for the film. Incorporating bells and dulcimers to exemplify the presence of new and old, Orvarsson's theme for Clary is inspired by New Age music with gypsy undertones. After attending a screening of the film's first cut, Orvarsson immediately presented Zwart with a piece of note paper. "He handed me music scribbles and said 'This is the theme' and it is the beautiful 'Clary's Theme' we hear in the film," said the director. The composer also incorporates the power of a choir throughout the score, creating the feeling of virtuosity and majesty while also utilizing the vocals to tell the darker tales of the Underworlders.